Nitriding of steel and titanium surface layers under the action of compression plasma flows

The elemental and phase compositions of St3 steel and VT1-0 titanium surface layers nitrided by the action of compression plasma flows (CPFs) have been investigated. The plasma flow parameters are shown to be correlated with the modified-layer nitrogen content. The basic mechanism by which the steel and titanium surface layers are saturated with nitrogen has been revealed. The performed experiments indicate that an increase in the absorbed energy density leads to a decrease in the nitrogen concentration because a shock-compressed layer is formed in the near-surface region, impeding nitrogen diffusion into the sample. The higher nitrogen concentration of surface layers treated by CPFs is achieved by increasing the pressure of the residual nitrogen atmosphere. It has been established that gamma(N)-Fe nitrous austenite, alpha aEuro(3)-Fe(N) and alpha'-Ti(N) martensitic phases, and gamma'-Fe4N and delta-TiN (x) nitrides can be produced by nitriding the surface layers of St3 steel and VT1-0 titanium.